The invention relates to a method for machining an integrally bladed rotor of a fluid-flow engine, specifically of an integrally bladed compressor rotor for a gas turbine.
Compressor rotors of gas turbines are increasingly designed as integrally bladed rotors. Integrally bladed rotors are also designated as a blisk (bladed disk) or a bling (bladed ring), depending on whether they have a disk-shaped main rotor body or an annular main rotor body. Because of manufacturing inaccuracies in the fabrication of integrally bladed rotors, the rotor blades of the integrally bladed rotor can demonstrate a natural frequency deviating from a desired natural frequency. The result of this can be that with forced vibrations during operation, amplitudes of vibration of individual rotor blades become unacceptably large so that during operation of the fluid-flow engine, or gas turbine, the risk of damage exists.
With this as the starting point, the problem underlying the present invention is to create a method for machining an integrally bladed rotor of a fluid-flow engine.
In accordance with the invention, the method comprises at least the following steps: a) providing an integrally bladed rotor having a main rotor body and several rotor blades integrally attached to the main rotor body; b) determining the natural frequency of each rotor blade of the integrally bladed rotor; c) machining at least one rotor blade of the integrally bladed rotor by removing material to adjust the natural frequency of the particular blade to a specific value.
In the meaning of the present invention, a method is provided with which it is possible to selectively affect the natural frequency of rotor blades on integrally bladed rotors. This makes it possible to reduce the stresses acting on the rotor blades during operation and thus on the integrally bladed rotor and to substantially reduce the risk of damage to the rotor.
The particular rotor blade of the integrally bladed rotor is preferably machined by removing material in the area of a radially inward lying section and/or in the area of a radially outward lying section and/or in the area of the leading edge and/or in the area of the trailing edge.
In the case in which a rotor without an outer shroud is provided as the integrally bladed rotor, the particular rotor blade of the integrally bladed rotor is machined by removing material in the area of a radially inward lying transition section between the main rotor body and the rotor blade and/or in the area of a radially outward lying blade tip section and/or in the area of the leading edge and/or in the area of the trailing edge.
If, on the other hand, a rotor with an outer shroud is provided as the integrally bladed rotor, the particular rotor blade of the integrally bladed rotor is machined by removing material in the area of a radially inward lying transition section between the main rotor body and rotor blade and/or in the area of a radially outward lying transition section between the outer shroud and rotor blade and/or in the area of the leading edge and/or in the area of the trailing edge.
In accordance with a first advantageous further development of the invention, the natural frequency of the particular machined rotor blade is adjusted such that all rotor blades have the same natural frequency.
In accordance with a second advantageous further development of the invention, the natural frequency of the particular machined rotor blade is adjusted such that periodically changing natural frequencies occur around the circumference of the rotor.
Preferred further developments of the invention emerge from the following description. Embodiments of the invention, without being restricted thereto, are explained in more detail using the drawings.